<!DOCTYPE html>
<html>
<head>
<style type="text/css">
.separator {
 height: 20px;
 background-color: green;
}
#spacer1 {
 height: 60px;
}
#min-height {
 height: 20px;
 background-color: blue;
}
#spacer2 {
 height: 40px;
}
</style>
</head>
<body>
<div class="separator"></div>
<div id="spacer1"></div>
<div id="min-height">
 <div id="zero-height"></div>
</div>
<div id="spacer2"></div>
<div class="separator"></div>
</body>
</html>
